get the USB version... install the program to a USB thumbdrive. Boot to the USB drive and let the memtest program run... (it will start automatically)
If you aren't looking at a screen like this you aren't testing your memory correctly.

It looks to me that given the image provided, your Google Chrome has a Memory Leak (
As you said Memtest86 says memory is working fine. (Memtest86 is the best) So given the 80% + Usage of your Memory in the system all taken up by the chrome executable. I would say your system is suffering from the results of the memory leak getting out of control over time, which results in memory thrashing.

I not only have seen this before when fixing computers, but have also succeeded repeatedly triggering the memory leak in chrome. (The same test on the same machined show Firefox did not have the same problem).

Depending on the amount of RAM you have available it can take some time before the memory thrashing becomes apparent. Usually a reboot will solve the issue for a short time.

My suggestions is to (backup stuff from chrome) and uninstall it. See if you problems continue.